1. Field of the Invention
This invention relates to foamable polymeric compositions which are especially useful as insulating, caulking and sealing compositions.
2. Description of the Prior Art
Insulating, caulking and sealing compositions are known in this art. These conventional compositions include a wide range of compounds which are used in the construction, manufacturing and transportation industries. These compositions are used to seal joints or voids against water and water vapor, air and other gases, dust, sound, vermin, heat and cold, and to insulate piping and heating systems to prevent heat loss. Specialized applications require resistance to certain chemicals or environments.
One type of caulking composition which has attained widespread popularity is the type based on polymers and mixtures of polymers. For example, U.S. Pat. No. 3,551,374 describes polymeric caulking compositions based on mixtures of polymers of esters of ethylenically unsaturated carboxylic acids having three to five carbon atoms, and alkanols having one to twelve carbon atoms. In general, these caulking and sealing compositions are prepared by melting together the components, by mixing solutions of the polymers, or by mixing suitable monomers with bitumen, tar or pitch and effecting polymerization when these mixtures are used.
These conventional caulking compositions are available in a variety of forms and packages, which are dependent on the form in which the composition is to be applied and its physical properties. For example, they are supplied generally in the form of knife- or gun-grade compositions. The knife-grade materials are the stiffer of the two, and lend themselves to putty-knife application. The gun-grade compositions are extruded through an orifice, using a hand or pressure-operated caulking gun. The use of aqueous polymer dispersions for gunnable or extruded caulking compositions is advantageous because such compositions are more easily applied, and because polymers having special properties are more easily prepared by emulsion polymerization. However, compositions of this type suffer from a number of disadvantages. Normally, these compositions are dispensed from a cartridge through use of a caulking gun. The need for a caulking gun increases the expense of using such compositions. Further, the cartridges in which the compositions are packaged are usually of the type having an enclosed plastic nozzle through which the composition is dispensed. When used, a portion of the plastic nozzle is cut off, forming a dispensing orifice which will dispense caulking composition in a certain ribbon size. This is disadvantageous because while more of the plastic can be cut off to form a larger dispensing orifice which results in a larger ribbon size, the size of the dispensing orifice cannot be restricted. As a result, the ribbon size of the caulking composition cannot be reduced at a later time.
Another disadvantage associated with the use of gunnable aqueous polymeric caulking compositions is that the high water content of the dispersion causes a marked shrinkage of the caulking seals prepared therewith. The composition which initially completely fills a gap later develops a concave surface. Although it is possible to add inorganic fillers to decrease the water content, and consequently to reduce the tendency of the compounds to shrink, the adhesive and cohesive properties of the emusion polymers are in general adversely affected by these additives. Also, when inorganic fillers are used, the viscosity of the caulking composition is increased such that the composition is difficult to use in situations where the composition must be deposited into small cracks.
Still another disadvantage associated with the conventional aqueous polymeric dispersion-based caulking composition is that the viscosity of such compositions is often so low that they cannot be effectively used in overhead situations because of the tendency of the composition to flow. Such properties can be cured by the addition of fillers, which results in the disadvantages discussed above.
Accordingly, there is a need for a polymeric caulking composition that cures the aforementioned disadvantages of the conventional knife and gun-grade compositions. Those of skill in the art have suggested the use of foam polymeric compositions for caulking and insulating.
One drawback of these compositions has been the difficulties associated with preparation of the foamed caulking material. Recently, foamable compositions have been prepared by mixing a polymer and a polymer-soluble inert blowing and propelling agent under pressure in an aerosol container. The blowing agent is usually a generally volatile organic liquid which vaporizes when released from the container, and thereby foams the polymeric material. For example, U.S. Pat. No. 3,640,916 describes foamed caulking and insulating compositions based on a cross-linked acrylic emulsion polymer and in which various hydrocarbons and halogenated hydrocarbons are employed as the blowing and propelling agents. These compositions have not been generally acceptable as caulking compositions because of various disadvantages associated with the physical characteristics of the resulting foam. The principle disadvantage is the expansion ratio of the above-mentioned foamable composition when released from the container. For example, experimentation has shown that these compositions expand to more than six times their volume when foamed with volatile liquid hydrocarbon and/or volatile liquid halogenated hydrocarbon blowing agents. This expansion ratio is so large that a small tight ribbon of foam caulking composition cannot be deposited. Another disadvantage relates to the physical state of the foam. Generally, the consistency of the foamed composition is such that it drips from vertical and overhead surfaces, and the composition is subject to collapse which causes considerable shrinkage of the composition after drying.
Accordingly, there is a need for a foamable caulking composition which obviates the defects of the known caulking compositions.
It is, therefore, an object of this invention to provide a foamable caulking composition which is resistant to environmental factors, and which adheres well and exhibits minimal shrinkage after drying.
It is also an object of this invention to provide an aerosol dispensed caulking composition which can be used in the home or in other like field environments and which can be dispensed in a tight ribbon.
It is yet another object of this invention to provide a foamable caulking composition which can be dispensed from an aerosol container in ribbons of varying sizes.
It is still another object of this invention to provide an aqueous polymeric based caulking composition which can be dispensed in small cracks or crevices.
It is yet another object of this invention to provide a foamable aerosol-dispensed, aqueous, polymer-based composition which forms a foam caulking composition which does not collapse unduly, and which does not drip from overhead or sag on vertical surfaces.
It is still another object of this invention to provide an aerosol container including the caulking composition of this invention, said container being adapted to dispense the composition.
Other objects and advantages will be apparent to one of skill in the art from the following description and appended claims.